 Kathy Thornton continues to ignite fuels that are, have been deployed onto a thin fiber. That's affirmative Val, this is a real nice drop and we'd like to continue on at step delta decimal five. Once again we are able to see experiment video from three of the experiments that are being processed on board space lab. Standby Rommel and Kathy can you confirm it's still burning? There's a little bit of crowding in the chamber this time and that was really strange looking. In space lab Huntsville for Kathy we are going to run with the FSDC fan on for this next three millimeter run and when you're ready to copy the setting I've got that for you. Kathy Thornton has just released another drop of fuel onto the fiber and the fuel has just been ignited. You can see the combustion products or soot that are being released by the burning fuel. The combustion products. Hello FACO and I'm from Worcester, Mass. I'm a PS on this flight in United States microgravity lab number two. We're doing a lot of science experiments at a whole variety of different fields, biotechnology, material science, crystal growth, fluid dynamics, fluid physics and combustion. And we're going to talk a little bit about all of these things with you guys today but before we do let me introduce or let them introduce themselves the redshift. First we'll go to our commander, the boss. Ken Ballersox, I'm from Bedford, Indiana and I'm the mission commander on STS-73. I'm the payload commander on this flight. And I'm Ken Rominger from Delano, Colorado and I'm the pilot on this flight. And that's the redshift. Okay for questions regarding fluid experiments, Worcester, South High please go ahead. This is Hosai Nagatsasham and my question is what is the purpose of the contact angle experiment? Other than to understand the purpose of the contact angle experiment you first have to understand two variables that are involved with it. One is called surface tension and the other is contact angle and they're related. Surface tension really can be simply thought of as how molecules like each other. If they like each other a lot they have a very high surface tension. On the other hand what you also have to balance is how they like the materials they contact. And those are called adhesive forces. Adhesive forces is how the liquids like the solid. So what you have when the contact angle experiment is a balance between what they call cohesive forces or surface tension and adhesive forces so how it likes the wall. And when those two balance and they're balanced by gravity that's really how far up the liquid goes. Now in space the reason we come to space to study surface tension is primarily because it dominates. Let me give you an example of that. You see in space the orange juice the molecules like each other and they form a sphere. If you were to do that on the ground of course it would cling to the sides of the vessel. And these are called again surface tension is something called a cohesive force. Susan Bellach from the Accelerated Learning Laboratory. Hi I'm Nick Pickett from North High School. Hi I'm Beth Quiladamo from North High School. Hi I'm Richie Hill from North High School. Hi I'm Josh Norver from Darity High School. Hi I'm Tanisha Woster from North High School. And our question is how does the surface tension in contact angle react in space when soap is added and why? What we call a surfactant and what that does is reduce the surface tension. And in space it reduces the surface tension by the same amount. It doesn't change at all in space. But again what you can see is you can see the effect of that surfactant a lot more in space because you have a 1-6 gravity component and therefore surface tension dominates over gravity and we can explore that. But it really doesn't change anything more than it does on the ground. The ground in space is very similar when you add soap as a surfactant. Hi I'm Katie Elworthy from Darity High School. Another question please. Hi I'm Igor Grilish from Darity High School. And I'm Todd DeVy from Darity High. And our question is in the contact angle experiment what would happen if the slides were of different materials and sizes and would other liquids change results? With what I've explained to you so far that surface tension and contact angle are basic properties of a liquid and its interaction with the solid. So those aren't affected by space. However every time you change the liquid or you change the solid that it's in contact with that is the material then you in fact will affect the contact angle experiment how high it rises. But the size that is the size of the materials or even the amount of liquid that you put in really doesn't have a major effect on that. Either in space or on the ground. Next question please. We have five minutes remaining in Worcester. Please go ahead with the next question. Hi my name is Hong Tran from North High and I was wondering if the mass of an object can break its surface tension. That's another very interesting question and you had to think about it a little bit. Surface tension again is a basic property of a fluid and it really doesn't change whether we have a large mass on it or a small mass on it, the surface tension is the same. However what you see is if I look at an eyedropper and I squeeze out a little bit of liquid on the ground as that liquid grows it gets very heavy and as it gets heavy it elongates the drop and eventually it falls off. Now the surface tension of that material didn't change it just became so heavy that the adhesive forces were overcome by the cohesive forces. Excuse me the cohesive forces were overcome by gravity is what I'm trying to say. Up here that wouldn't happen of course and you saw that with the straw when I squeezed out the orange juice it just sort of hung there in the sphere. So surface tension really doesn't change it's not broken by mass but it looks that way and it seems that way because of your observation of the one gravity environment. Hi my name is Yola Tafani from South High. My question is is there a difference in the velocity of the spreading pepper in space? To be honest with you we didn't spread any pepper in space on this flight at least we haven't yet but I would expect that there may be a difference in velocity and the difference in velocity wouldn't be because of the surface tension effect but because of convective effects temperature differences and that's additive so you get not only the surface tension effect but in addition to that you may get some convective effect so you probably see a difference in the velocity of the pepper itself moving across the surface. But another question please. We have one minute left and what's your time for one last question? For every action there's a reaction would a ball of water disperse if you put pepper into it? Well we haven't run that experiment either but I can tell you the answer to that just like sprinkling pepper on a liquid surface what you'd see up here is you'd see the pepper just form around the outside of the sphere of liquid and for every action there is a reaction as the pepper touches the surface of the liquid the liquid would touch back with exactly the same force but what you'd see is because of surface tension that pepper would just adhere to the outside of the drop and it would form all the way around the drop you'd see a uniform distribution of pepper all the way around the drop. Hi my name is Prubali Chakraborty and can fiber supported drop combustion be used in the shuttle's engines to make maneuvering simpler and are there any real life applications? That's a good question too and I have an aviator here and a fighter pilot that's going to answer that for us and also the pilot of the shuttle and this is a cat. Thanks Ali, that's a great question and the answer is maybe that can help us maneuver the shuttle and also in real life applications are many I'll start out by saying as well as the shuttle from having better combustion and the F-14 I used to fly as well as the car that people drive even the heater and water heater in your home it can help them be much more efficient and the reason we studied that up here in microgravity is without the influence of gravity and without convection the burning is much more even in a sphere and it bursts more slowly so we can control it and much better analyze it and hopefully come up with more efficient combustion processes and fuels and additionally that would also result in less pollutants so it would help the environment also. Next question. Hello my name is Jill Fackler do different flammable liquids form different shapes when they burn and are the materials you're using different from ours? Two good questions, I understand the materials that you are using are petroleum distillate which is a mixture of all different kinds of petroleum products we're trying some pure fuels up here or very simple mixtures we're using some methanol and water and a few other mixtures and because they are liquids they form a sphere here in space just like the orange juice you saw floating around but we don't want these burning droplets floating around the space lab so we can find them by putting them on a fiber so there are spherical drops on a fiber the different materials are formed in the same shape however the combustion of the different materials is significantly different the methanol was burning with a very very faint blue shell of flame and some of the other products were burning with yellow blue and yellow alternating kind of flames You have another question? Yes my name is Jessica Huddy did your flames move around or vary in size and shape due to air currents and do the flames produce any visible products such as smoke? That's a very good question some of the things that we're trying to explore up here we have done some of the burns without air currents and we get a completely spherical shell of flame and others we have done with air currents and we get a teardrop shape where the combustion products and the vapors that are burning are moving along with the air currents it also changes the color of the flame because with air currents we're feeding more oxygen to the ball of fire and when we're not having air flow the oxygen has to diffuse into the combustion zone so it's a little bit slower burning process it also burns bluer whereas with air flow we have a little bit of a yellow color which is Ray Marquette what percentage of time did you get a good flame and how long on average did your flames last? We've had a little bit of trouble getting the droplets deployed on the fiber but once we get them on the fiber we get ignitioned every time and it burns from on the average of 5 or 6 seconds for a small drop to a 5 millimeter drop which is going as long as 25 or 30 seconds which is a lot longer burn time than you're getting on the ground with your experiment Hi my name is Geraldine Waters and my question is do you think anything besides the difference in gravity could cause the flames to differ? A lot of effects on this experiment and yours in your experiment you're burning a teardrop shaped fuel because gravity is pulling it down here we start out with a spherical drop of fuel and also because of convection which is another effect of gravity the combustion products and actually the vapors that are burning are rising in your experiment and oxygen continues to be supplied from the bottom here we don't have that so we're looking at diffusion of oxygen into the flame front to continue to feed it which is a little bit different than what you're doing so gravity is certainly the major effect up here but the lack of gravity is the difference in what we're doing and what you're doing down there My name is Jared Shooter Do you have to replace the filament after each time that you burn the fluid? Not a good question We didn't replace the filament every time but we do replace it periodically and one of the reasons for that is we get soot deposits we get carbon deposits high molecular weight carbon materials and what do they do? They change the surface tension of the liquid and how it interacts with the solid itself that can result in a variety of different things not the least of which is the drop moving along the filament itself in addition to that it can change the heat transfer rate how heat is leaving the filament which affects the studies that we're looking at so we don't replace it all the time but if it looks like it's getting a little sooty then we do in fact replace it My name is Kate Gayhart Does the type of filament have an effect on the result of the experiment? Yeah, very much and that's another very interesting question because one of the things that we're looking at is all the different heat transfer and mass transfer effects how oxygen comes into the flame and that light blue flame that we see is a result of what we call a diffusive flame Oxygen is not convecting in by other molecules as a group but coming in individually is a diffusive flame How the heat is taken out of the filament is very important because some of the heat is being conducted down the filament so if we change that material we can change it from a metal which is very conductive to a ceramic which we're using up here which is a little bit less conductive and that changes the entire burning rate of the flame and changes what we see and the dynamics of the flame itself and the thickness of that material are very very important it's also important in microgravity to make sure again the liquid and the solid are compatible in the sense that the liquid to a certain extent but not too much lets the solid in other words we don't want it to like the solid too much so it won't maintain its ferricity but we'll spread along the filament but we do want it to maintain its contact with the filament we need to like the filament a little bit and John C. my question is is the flame isolated to the coil of the filament or does it move away from the filament so just the fluid is burning first again when I'm using a coil up here we're using a filament just a straight line I'll remember from studying this that in fact the liquid is not burning but the vapor is from the liquid of burning and that's what we see as well we see a shallow halo of burning material that's displaced slightly from the liquid of the fuel that burns the vapor and this is the last question from Louisville Science Center please go ahead my name is Tom Fulda and I was wondering with the amount of electricity used in the experiment changed the rate of combustion and would microgravity have any effect on this? that's another interesting question we have to think on that a little bit but certainly when you put in more electricity into your filament now we're not doing it exactly that way we're igniting it from an external source we're not doing electricity through it I wouldn't expect the electricity to be affected by the microgravity at all but by increasing the electricity in the filament if we were doing it that way like you're doing it on the ground increases the rate at which the filament heats and therefore impacts the rate at which the vapor is combust so in fact as you change the electricity you may see an effect but that would be again a function of the material that you make your coil out of and the rate at which you put electricity in it would be a very subtle and difficult thing to measure for you but it is measurable on the ground and microgravity that wouldn't affect us very much first of all because of the way we're doing the experiment but in addition to that even if we were using an electrical way to heat this filament I wouldn't expect microgravity to affect electricity very much up here so that in and of itself would not be affected by microgravity the same thing that was affected on the ground though would be affected up here the rate at which you put the electricity in how much the thickness of the material and what that material is how much of a conductor it is will in fact affect that burning rate